Video Card for Dual 22-inch Moniters

I just bought two 22-inch Dell moniter's on sale. I want to buy a video card that will give me the best performance within a reasonable price range ($50-$200). Is there anyone can tell me which one to buy? Do I have to buy the one with Dual DVI as well?

Another question: Is there any difference between 4G and 3G? (My system is Vista)